Jaw-actuating means for pipe tongs

ABSTRACT

Jaw-actuating means for pipe tongs in which a roller is interposed between a pair of relatively movable cam surfaces for actuating a jaw into gripping engagement with a pipe joint, the roller being initially resiliently centralized in engagement with one of the cam surfaces and out of engagement with the other cam surface, but the roller shifting to engage both cam surfaces upon actuation towards a pipe-engaging position.

United States Patent 72] Inventor Howard S. Flick Long Beach, Calif. [21 1 App]. No. 851,663 [22] Filed Aug. 20, 1969 [45] Patented June 29, 1971 73] Assignee Byron Jackson Inc.

Long Beach, Calil.

s4 1 i wlxcmm MEANS FOR PIPE TON'GS 16 Claims, 14 Drawing Figs.

52 U.S.Cl 279/71,

269/235, 279/1 14, 81/57.]8 s11 lnt.Cl. ..B23b3l/l6 so FieldofSearch .279/66,'l

[ I 7 References Primary Examiner-Andrew R. .luhasz Assistant ExaminerP-James F. Coan Attorneys-Donald W. Banner, William S. McCurry and John Y W. Butcher ABSTRACT: Jaw-actuating means for pipe tongs in which a roller is interposed between a pair of relatively movable cam surfaces for actuating a jaw into gripping engagement with a pipe joint, the roller being initially resiliently centralized in engagement with one of the cam surfaces and out of engagement with the other cam surface, but the roller shifting to engage both cam surfaces-upon actuation towards a pipe-engaging 81/57.1, 5' l.11,57.l8,57.2l;29[240 position.

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ATTOEA/B PATENTED JUH29 IQYI SHEET 6 BF 7 INVEN'IOR HOW/4E0 s. a ma B .IAW-ACTUATING MEANS FOR PIPE TONGS BACKGROUND OF THE INVENTION In the making-up and breaking-out of well pipe or rod joints, such as the threaded joints of drill pipe, tubing, casing, or sucker rods, all referred to herein for simplicity asjoints or pipe joints, it has been the practice, in many cases, to employ a power tong for turning one pipe or joint part, while the other joint part or pipe is held against rotation by a'backup tong. Various jaw devices and jaw-actuating means have been utilized, both for actuating the jaws of the power tong and the backup tong. The jaws are initially or normally retracted to allow movement of a joint part into or through the tong, but when the joint part is to be gripped, the jaws are actuated toward one another.

A common mode of effecting closure of the jaws on a pipe is the use of an angularly movable member, a cam, and a cam follower, interposed between the jaws and the angularly movable member to move the jaws radially inward or toward one another to grip the pipe or joint part between the jaws, the radial component of force on the jaws being a function of the cam angle. In order to drive the pipe joint in opposite directions, the power tong must either be rolled over, or it must have oppositely extended cam surfaces which are effective to close the jaws upon angular movement of the angularly movable member in either direction. Rolling the power tong over may be objectionable and in some instances is impossible, if, for example, the tong is circumferentially continuous and is disposed about the pipe.

Such tongs, moreover, are preferably adaptable to use on joints over a wide range of diameters with a minimum of interchangeability of parts, such as die holders or jaws. However, when the angularly movable member has oppositely inclined cam surfaces to provide for jaw closure in both directions of angular movement of the member, a problem is encountered respecting the size of the tong assembly, on the one hand, or, on the other hand, the permissible range of sizes ofjoints which can be effectively gripped by the jaws without modification of the jaws. The cam surfaces are generally on the angularly movable member and are long arcs, the slope of which governs the radial force applied to the jaw and thus the effectiveness of the gripping of the pipe by the jaws. Within a given tong size, if the cam slope is such as to enable a wide range of jaw movement, for use in gripping a wide range of joint diameters, the slope is so steep that insufficient radial force can be applied to the joint to effectively grip the same. This is a problem which can be obviated by reducing the slope of the cam surface, but, then, the range ofjaw movement is inherently reduced.

SUMMARY OF THE INVENTION The present invention provides jaw-actuating means for tongs of the general type referred to above, wherein the jaws are actuatable to grip a wide range of joint diameters, without requiring modification of the jaws, responsive to angular movement of the angularly movable member in either direction, and wherein a second cam surface cooperates with the follower to increase or intensify the radial component of force on the jaws after the jaws initially engage the pipe.

More particularly, the present invention involves the use of, a roller follower carried by a jaw and engageable with the cam surface, the follower being rotatable on an axle which is resiliently centralized, so that during initial movement of the jaw the roller revolves about its axis and moves the jaw toward the joint part, but following the engagement of the jaw with the pipe, the roller is shifted to also engage another surface on the jaw and opposed to the cam surface on the angularly movable member. Thereafter, the roller will roll along both of these surfaces, so that the radial component of force produced by the cam surface is increased as a function of the angular relationship of the two opposing surfaces engaged by the roller, and the axle of the roller is shifted from its initial position.

An object of the invention, then, is to provide a tong which is operable to grip pipe or points over a wide range of sizes or diameters, while providing intensified radial forces on the jaws to effectively grip the pipe and prevent slipping of the jaws with respect to the pipe.

This invention possesses many other advantages, and has other purposes which may be made more clearly apparent from a consideration of forms in which it may be embodied. These forms are shown in the drawings accompanying and forming part of the present specification. They will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed descriptions are not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims. 1

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view illustrating a tong assembly incorporating the invention;

FIG. 2 is an enlarged top plan of the tong head with parts broken away;

FIG. 3 is an enlarged vertical section as taken on the line 3-3 of FIG. 2;

FIG. 4 is a horizontal section on a reduced scale as taken on the line 4-4 of FIG. 3;

FIG. 5 is a fragmentary view in vertical section, as taken on line 5-5 of FIG. 3, through one of the pipe-gripping jaws;

FIG. 6 is a horizontal section, as taken on the line 6-6 of FIG. 5, showing one of the jaws in the fully retracted position;

FIG. 7 is a view corresponding to FIG. 6, but showing the jaw actuated into initial gripping engagement with the pipe;

FIG. 8 is a view corresponding to FIGS. 6 and 7, but showing the jaw actuated into tight gripping engagement with the pipe;

FIG. 9 is a fragmentary vertical section as taken on the line 9-9 of FIG. 4, showing the reverse stop mechanism;

FIG. 10 is a fragmentary vertical section as taken on the line 10-10 ofFIG. 9;

FIG. 11 is a plan view ofa modified jaw mechanism with the jaw in a fully retracted position;

FIG. 12 is a detailed view in vertical section, as taken on the line 12-12 of FIG. 11;

FIG. 13 is a view corresponding to FIG. 11, but showing the jaw actuated into initial gripping engagement with the pipe; and

FIG. 14 is a view corresponding to FIGS. 11 and 13, but showing the jaw further actuated into tight gripping engagement with the pipe. 4

DESCRIPTION OF THE PREFERRED EMBODIMENTS As seen in the drawings, a power tong assembly T has a tong head I-I adapted to be disposed about a length of pipe P. The tong assembly T includes at least one motor M for operating the tong head under the control ofa control mechanism C, so that the tong head will gripthe pipe P and rotate the same in either direction, depending upon whether it is desired to makeup or breakout ajoint .l which connects a lower length of pipe P1 to the length of pipe P, all as is well known in the art.

The details of the tong assembly in general are not germane to the present invention, which involves the mode of actuation of the pipe-gripping mechanism included within the tong head 1-1.

More particularly, the tong head subassembly comprises a housing or case I having an upper case section 2 and a lower case section 3 interconnected by a suitable number of peripheral fasteners 4. A driven gear 5 extends into the case 1 and is in mesh with a ring gear 6 which constitutes an outer rotary ring and which is supported for rotation in the case 1 by upper bearings 7 and lower bearings 8. An inner ring assembly includes upper and lower plates 9 and 10 joined together, as seen in FIG. 9, by a suitable number of fasteners 11. The inner ring plates 9 and 10 define a central pipe opening 12 therethrough. The upper plate 9 of the inner ring assembly ineludes an outer marginal flange 13 which is slideably disposed on the annular body 14 of the outer ring or ring gear 6, whereby the inner ring is supported on the outer ring for relative rotation during the operation of the pipe-gripping means, hereinafter to be described.

The pipe-gripping means, in the tong head now being described, comprises a pair of radially shiftably disposed jaws 15, 15 which are reciprocably disposed in windows 16 defined by the inner ring plates 9 and 10. A typicaljaw 15 is best illustrated in FIG. 4, 5 and 6 as comprising a body 17 having a die carrier 18 supported thereon by means of a spherical joint at 19 and retainer pins 20 which are threaded into the die carrier 18 and have their upper ends 21 and their lower ends 22, respectively, loosely disposed in openings 23 and 24 in the jaw body 17, whereby the die carrier 18 is free to partake of limited universal movement. The die carrier 18 included dovetailed slots 25 adapted to receive two tong dies 26 provided for the purpose of gripping the pipe P to rotate the same upon actuation of the jaws into gripping engagement with the pipe P.

The jaws are normally spring biased to retracted positions within the windows 16. Accordingly, each jaw body 17 is provided with outstanding cars 27 on opposite sides thereof engaged by U-shaped connectors 28. The ends 29 of the connectors 28 are turned back and are provided with spring seats 30 on which seat coiled compression springs 31. These coiled compression springs 31 extend into spring-seating bores 32 in the respective inner ring plates 9 and 10. Thus, the springs 31 normally act to move the jaws outwardly to their retracted positions.

The outer ring or ring gear 6, as best seen in FIG. 4, has a cam surface generally indicated at 33 thereon engageable with cam followers or rollers 34 carried by the jaw body 17, whereby upon relative rotation of the outer ring or ring gear 6 and the inner ring assembly 9 and 10, the jaws 15 will be actuated inwardly to projected or pipe-gripping positions.

More particularly, the cam surface '33 is a compound cam surface which is symmetrical and includes opposite cam portions 33a adapted to engage the rollers 34 upon rotation of the outer ring or ring gear 6 in a clockwise direction to make up pipe joints, and the cam surface 33 also includes opposing cam portions 33b adapted to engage the rollers 34 when the outer ring or ring gear 6 is rotated in a counterclockwise direction to break out joints of pipe. Intermediate the cam surface portions 33a and 33b are central depressions 330 in which the rollers 34 are disposed when the jaws 15 are fully retracted, as seen in FIG. 4.

In order to resist initial rotation of the inner, jaw-carrying ring assembly with the outer ring 6, so that the cam surfaces and rollers may effect actuation of the jaws 15 from the retracted positions to the pipe-engaging positions, a brake band 35 having friction facing material 36 thereon is disposed within the case section 2 and is adapted to engage an annular surface 37 on a flange 38 of the inner ring plate 9. Referring to FIG. 2, it will be noted that the brake band 35 is suitably anchored by an anchor lug 39 which is welded or otherwise secured to the band 35 and has a vertical slot 40 adapted to receive a lug 41 provided within the outer case section 2. The brake band 35 has end ears 42 through which a brake adjuster screw 43 extends. A coiled spring 44 is disposed about the screw 43 and acts on one of the cars 42 and on the head of the adjuster screw 43 to supply a spring force tending to normally hold the brake band in frictional engagement with the annular face 37 of the inner ring assembly. Accordingly, initial rotation of the inner ring assembly is prevented so that angular movement of the outer ring or ring gear 6 relative to the inner ring assembly will cause the rollers 34 to engage either the cam faces 33a or the cam faces 33b depending upon the direction of rotation of the outer ring 6, whereby to cam the jaws 15 toward pipe-gripping positions.

After the pipe has been gripped by the jaws, then the brake means, described above, will slip to allow rotation of the inner ring assembly along with the driven outer ring or ring gear 6, whereby to impart corresponding rotation to the pipe P.

When, following rotation of the pipe P in one direction, it is desired to release the jaws from gripping engagement with the pipe, the outer ring or ring gear 6 is rotated in the opposite direction, until the cam rollers 34 are disposed in the depressions 33c Reverse stop means are provided to limit such rotation of the outer ring relative to the inner ring, so that the jaws 15 will not be reversely actuated to reengage the pipe P. This reverse stop means is best illustrated in FIGS. 4, 9 and 10, as comprising a traveling stop pin 50 which is carried by and extends downwardly beneath the outer ring or ring gear 6. The stop pin 50 is adapted to abut with either a makeup reverse stop .51 or a breakout reverse stop 52 which are respectively reciprocably disposed in chambers 53 and 54 formed in the plate 10 of the inner ring assembly 9, 10. A spring 55 is disposed behind the inner end of the makeup reverse stop 51 and a similar spring 56 is disposed behind the inner end of the breakout reverse stop 52, so as to normally bias these stops outwardly into the path of the traveling stop 50. An actuator ring 57 is provided, having an inner peripheral flange 58 which is supported on a retainer ring 59, the ring 59 being carried by a downwardly extended annular flange 60 on the inner ring assembly plate 10. This actuator ring 57 has a cam surface 61 thereon which engages an actuator pin 62 projecting downwardly from the reverse stop 51 and another actuator pin 63 which projects downwardly from the reverse stop 52. The cam surface 61 includes a section 64 having a depression 65 which will hold the actuator ring 57 against inadvertent movement and which will hold either of the reverse stops 51 or 52 retracted. In FIG. 4 the actuator pin 63 is shown as engaged in the depression 65. When it is desired to allow the reverse stop 52 to be projected and the reverse stop 51 retracted, the actuator ring 57 is rotated in a clockwise direction, releasing the reverse stop 52; then the cam surface 61 will cause progressive retraction of the reverse stop 51. When either of the stops 51 or 52 is in the projected position, reverse rotation of the outer ring or ring gear 6 relative to the inner ring assembly is limited to a position at which the rollers 34 are in the depressions 33c of the outer ring cam surface 33, and thereafter the outer ring 6 and the inner ring assembly will rotate as a unit with the jaws fully retracted.

The details of the tong assembly, as thus far described, are not germane to the present invention except that the assembly functions to effect movement of the pipe-gripping jaws 15 between the retracted positions and the pipe-gripping positions in response to angular movement of the outer ring in either direction. Slnce the cam surface 33 of the outer ring 6 is a compound cam surface, operable upon angular movement of the outer ring in either direction, the effective range of the operability of this type of tong has heretofore been limited, unless the jaws were modified by the provision of adapters or die carriers to cooperate with different sizes of pipe. The problem experienced by this type of tong involves the necessity that the cam surfaces of the outer ring not only provide for the gross movement of the pipe-gripping jaws, regardless of the size of pipe to be gripped, but also the same cam surfaces operate to cause gripping engagement of the dies with the pipe. Under these circumstances, the gripping effectiveness may be insufficient to provide the desired or necessary radial component of force tending to grip the pipe with the jaws. The present invention is more particularly concerned with the structure whereby the radial force tending to cause the gripping of the pipe by the jaws is enhanced or intensified.

Referring to FIGS. 5 through 8, the radial force intensifier is more particularly illustrated in one embodiment of The invention. In this form the cam roller 34 is rotatably mounted upon a shaft 70, the opposite ends of which extend through enlarged openings 71 in the jaw body 17. The roller 34 in each jaw is disposed in a laterally opening slop 72 which terminates in a face 73 opposed to the cam surface 33 of the outer ring 6. Means are provided for resiliently holding the rollers 34 in engagement with the cam surface 33 but spaced from the opposing jaw surfaces 73, as seen in FIGS. 5 and 6. In the embodiment now being described, a pair of shoes 74 is provided. The shoes 74 are reciprocable in upper and lower grooves 75 in the jaw body 17. A suitable number of coiled compression springs 76 is interposed between the inner wall of the grooves 75 and the shoes 74 so as to normally bias the shoes 74 outwardly into engagement with the roller shaft ends. Each shoe 74 is indented or provided with opposing angular faces 77 converging to form a detent 77a (FIG. 8) which engages with one of the shaft ends, so that the shaft ends will normally be centralized with respect to the shoes 74 and the rollers 34 will normally be spaced from the jaw faces 73. However, the rollers 34 may shift withing the shoe slots 75 and ride up the inclined surfaces in either direction. Accordingly, the springs 76 essentially function to centralize the rollers 34 with respect to the shoes 74 under normal circumstances.

However, when the outer ring 6 is rotated relative to the inner jaw-carrying ring assembly, say in a direction to make up pipe, the jaws will first be actuated inwardly by the action of the cam surfaces 33a on the radius of the respective rollers 34, until the dies 26 contact the pipe P, as seen in FIG. 7, at which time the rollers 34 will be interengaged between the cam surface 33a and the surface 73 of the jaw body 17 across the diameter of the rollers 34. At this point, the force tending to cause the jaws 15 to grip the pipe becomes a function ofthe relationship between the slope of the cam surface 33a and the opposing jaw surface 73. This jaw surface 73 is herein illustrated as being on a plane normal to the radial direction of the travel of the jaws 15, but since the force acting to cam the jaws inwardly is a function of the relationship of the cam surfaces 33a and the jaw surface 73, it will be appreciated that the surface 73 may itself be disposed on an angle or on an arc to cause the desired radial component of force with the selected slope of the cam surface 33a or 33b, as the case may be.

In this connection, it will be noted in FIG. 8 that following initail engagement of the die 26 with the pipe, and responsive to continued angular movement of the outer ring 6, the rollers 34 roll between the cam surface 33a or 33b, depending upon the direction of the rotation of the outer ring 6. The rollers 34 effectively shift within the slots 75, and the shaft 70 will ride up one of the angular shoe faces 77. Under some circumstances of maximum die penetration into the pipe P, the shafts 70 may abut with the side of the shoe slot 75, at which point further penetration of the dies into the pipe P will be limited. When the outer ring 6 is reversely rotated to retract the jaws, the springs 76, acting on the shoes 74, will again center the rollers 34 with respect to the inclined surfaces 77 of the shoes 74.

Referring to FIGS. 11 through 14, a modified construction is illustrated, wherein, in lieu of the shoes 74 and the springs 76 for centralizing the rollers 34 in the slots 75, a body 174 of resilient deformable material is disposed in each slot 75, so as to be engaged with an end of the respective roller shafts 70. The resilient deformable material may be polyurethane or other suitable material having opposed inclined surfaces 177 forming a detent 177a, whereby to centralize the roller shafts 70 when the jaws 15 are retracted and until sufficient force is applied to effect coengagement 0f the rollers 34 between the cam surfaces 330 or 33b, as the case may be, and the jaw surface 73, as seen in FIG. 13. Thereafter, further angular movement of the outer ring 6 will effect transverse displacement of the rollers 34 and resilient deformation of the pads or bodies 174, as seen in FIG. 14.

While two illustrative embodiments have been shown, it will be understood that the essence of the invention is the provision of the resilient means such as the shoes 74 andthe springs 76 or the deformable resilient bodies 174 to normally maintain the rollers 34 spaced from the jaw surface 73, but to allow coengagement of the rollers 34 with the jaw surface 73 upon initial gripping engagement of the jaws 15 in a radial pipe; whereupon, the forces acting on the jaws 15 in a radial pipegripping direction become a function, not of the radii of the rollers 34 and the slope of the cam surface 330 or 33!), but, instead, the radial gripping force is a function of the relationship between the slope of the cam surfaces 330 and 33b and the jaw surfaces 73. Initially, the rollers 34 act only on their radii, but

following shifting of the rollers 34 into engagement with the jaw surfaces, the rollers act substantially across their diameters.

I claim:

1. In a tongfor making up and breaking out pipe joints and the like: a support structure having an opening for a pipe, a pipe-gripping assembly including a number of pipe-gripping jaws movable between retracted positions and positions projecting into said opening in gripping engagement with said pipe, an angularly movable member, and jaw-actuating means for moving said jaws to said positions in gripping engagement with said pipe responsive to angular movement of said angularly movable member: the improvement wherein said last mentioned means comprises opposing surfaces on said jaws and said angularly movable member, rollers interposed between said surfaces, and resilient means initially holding said rollers spaced from one of said opposing surfaces, said rollers engaging said one of said opposing surfaces and rolling between said opposing surfaces following initial gripping engagement of said jaws with said pipe, whereby the force for gripping said pipe between said jaws is a function of the angular relationship between said opposing surfaces.

2. In a tong as defined in claim 1, said resilient means initially holding said rollers spaced from the surface on said jaws.

3. In a tong as defined in claim 1, said rollers having shafts supporting the rollers for rotation, said resilient means initially acting on said shafts to resiliently hold said shafts against lateral movement until said rollers roll between said surfaces.

4. In a tong as defined in claim I, said rollers having shafts supporting the rollers for rotation, and said resilient means including bodies of resiliently deformable material engaged with said shafts for initially resiliently holding said shafts against lateral movement until said rollers roll between said surfaces.

5. In a tong as defined in claim 1, said rollers having shafts supporting the rollers for rotation, said resilient means including shoes engaged with the ends of said shafts, and springs acting on said shoes to initially resiliently hold said shafts against lateral movement relative to said shoes until said rollers roll between said surfaces.

6, In a tong as defined in claim 1, said rollers including shafts supporting said rollers for rotation, said resilient means including bodies of resiliently deformable material engaged with said shafts and initially holding said rollers spaced from the surfaces on said jaws and against lateral movement of said shafts until said rollers roll between said surfaces.

7. In a tong as defined in claim 1, said rollers including shafts supporting said rollers for rotation, said resilient means including shoes engaged with the ends of said shafts, and springs acting on said shoes and initially holding said rollers spaced from the surfaces on said jaws and against lateral movement of said shafts relative to said shoes until said rollers roll between said surfaces.

8. In a tong as defined in claim 1, said resilient means including a member resiliently cooperably engaged with said rollers and initially holding said rollers spaced from the surface on said jaws and having detent means resiliently resisting rolling movement of said rollers between said surfaces following engagement of said rollers with the surface of said jaws.

9. In a tong as defined in claim I, said rollers having shafts supporting the rollers for rotation, said resilient means having detent means engaged with the ends of said shafts and resiliently resisting rolling movement of said rollers between said surfaces following engagement of said rollers with the surface on said jaws.

10. In a tong as defined in claim 1, said rollers having shafts supporting the rollers for rotation, said resilient means comprising bodies of resilient material engaged with the ends of said shafts and having a depression in which the ends of said shafts are initially disposed for resiliently resisting rolling movement of said rollers between said surfaces following engagement of said rollers with the surfaces on said jaws.

11. In a tong as defined in claim 1, said rollers having shafts supporting the rollers for rotation, said resilient means including shoes, means mounting said shoes for movement relative to said jaws, springs biasing said shoes into engagement with the ends of said shafts, and said shoes having depressions in which the ends of said shafts are initially disposed for resisting rolling movement of said rollers between said surfaces following engagement of said rollers with the surfaces on said jaws.

12. In a tong for making up and breaking out pipe joints and the like: a support structure having an openingfor a pipe, an outer ring revolvably supported by said support structure, an inner ring revolvably supported by said outer ring, a plurality of radially shiftable jaws carried by said inner ring for gripping a pipe disposed in said opening, and means for shifting said jaws radially between pipe-gripping and retracted positions, rollers carried by said jaws, oppositely sloped cam surfaces on said outer ring engaged with said rollers for moving said jaws; towards said pipe-gripping positions upon rotation of said v outer ring in either direction relative to said inner ring, and

means for retracting said jaws upon movement of said outer '1 holding said rollers spaced from said surfaces on said jaws, said resilient means being deformable to allow rolling movement of said rollers between said cam surfaces and said surfaces on said jaws following initial engagement of said jaws with said pipe.

13. ln a tong as defined in claim 12, said resilient means comprising bodies of resiliently deformable material, said rollers having shafts engaged by said bodies.

14. In a tong as defined in claim 13, said bodies of resiliently deformable material being composed by polyurethane.

'15. In a tong as defined in claim 12, said rollers having shafts, shoes slidably supported by said jaws and engaged with said shafts, and said resilient means comprises springs acting on said shoes.

16. In a tong assembly as defined in claim 12, said rollers having shafts having end portions projecting from said rollers, said jaws having slots into which said ends of said rollers extend, and said resilient means being disposed in said slots and acting on the ends of said shafts.

Patent No. 3,589 7M Dated une 29, 1971 lnventorc S.

It is certified that: error appears in the above-identified patent and that said Letters Patent are hereby corrected as shownxbelow:

Col. 2, line 2, "goints" should be --joints--. Col. 3, line 16, included" should be --includes--. Col. line 69, "slop" should be ---slot---.

001. 5, line 69, in a radial pipe" should read --with the pipe--.

Signed and sealed this 22nd day of February 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

1. In a tong for making up and breaking out pipe joints and the like: a support structure having an opening for a pipe, a pipegripping assembly including a number of pipe-gripping jaws movable between retracted positions and positions projecting into said opening in gripping engagement with said pipe, an angularly movable member, and jaw-actuating means for moving said jaws to said positions in gripping engagement with said pipe responsive to angular movement of said angularly movable member: the improvement wherein said last mentioned means comprises opposing surfaces on said jaws and said angularly movable member, rollers interposed between said surfaces, and resilient means initially holding said rollers spaced from one of said opposing surfaces, said rollers engaging said one of said opposing surfaces and rolling between said opposing surfaces following initial gripping engagement of said jaws with said pipe, whereby the force for gripping said pipe between said jaws is a function of the angular relationship between said opposing surfaces.
 2. In a tong as defined in claim 1, said resilient means initially holding said rollers spaced from the surface on said jaws.
 3. In a tong as defined in claim 1, said rollers having shafts supporting the rollers for rotation, said resilient means initially acting on said shafts to resiliently hold said shafts against lateral movement until said rollers roll between said surfaces.
 4. In a tong as defined in claim 1, said rollers having shafts supporting the rollers foR rotation, and said resilient means including bodies of resiliently deformable material engaged with said shafts for initially resiliently holding said shafts against lateral movement until said rollers roll between said surfaces.
 5. In a tong as defined in claim 1, said rollers having shafts supporting the rollers for rotation, said resilient means including shoes engaged with the ends of said shafts, and springs acting on said shoes to initially resiliently hold said shafts against lateral movement relative to said shoes until said rollers roll between said surfaces. 6, In a tong as defined in claim 1, said rollers including shafts supporting said rollers for rotation, said resilient means including bodies of resiliently deformable material engaged with said shafts and initially holding said rollers spaced from the surfaces on said jaws and against lateral movement of said shafts until said rollers roll between said surfaces.
 7. In a tong as defined in claim 1, said rollers including shafts supporting said rollers for rotation, said resilient means including shoes engaged with the ends of said shafts, and springs acting on said shoes and initially holding said rollers spaced from the surfaces on said jaws and against lateral movement of said shafts relative to said shoes until said rollers roll between said surfaces.
 8. In a tong as defined in claim 1, said resilient means including a member resiliently cooperably engaged with said rollers and initially holding said rollers spaced from the surface on said jaws and having detent means resiliently resisting rolling movement of said rollers between said surfaces following engagement of said rollers with the surface of said jaws.
 9. In a tong as defined in claim 1, said rollers having shafts supporting the rollers for rotation, said resilient means having detent means engaged with the ends of said shafts and resiliently resisting rolling movement of said rollers between said surfaces following engagement of said rollers with the surface on said jaws.
 10. In a tong as defined in claim 1, said rollers having shafts supporting the rollers for rotation, said resilient means comprising bodies of resilient material engaged with the ends of said shafts and having a depression in which the ends of said shafts are initially disposed for resiliently resisting rolling movement of said rollers between said surfaces following engagement of said rollers with the surfaces on said jaws.
 11. In a tong as defined in claim 1, said rollers having shafts supporting the rollers for rotation, said resilient means including shoes, means mounting said shoes for movement relative to said jaws, springs biasing said shoes into engagement with the ends of said shafts, and said shoes having depressions in which the ends of said shafts are initially disposed for resisting rolling movement of said rollers between said surfaces following engagement of said rollers with the surfaces on said jaws.
 12. In a tong for making up and breaking out pipe joints and the like: a support structure having an opening for a pipe, an outer ring revolvably supported by said support structure, an inner ring revolvably supported by said outer ring, a plurality of radially shiftable jaws carried by said inner ring for gripping a pipe disposed in said opening, and means for shifting said jaws radially between pipe-gripping and retracted positions, rollers carried by said jaws, oppositely sloped cam surfaces on said outer ring engaged with said rollers for moving said jaws towards said pipe-gripping positions upon rotation of said outer ring in either direction relative to said inner ring, and means for retracting said jaws upon movement of said outer ring in the other direction, the improvement comprising surfaces on said jaws engageable by said rollers following initial engagement of said jaws with said pipe, and resilient means for holding said rollers spaced from said surfaces on said jaws, said resilient means being deformable to allow rolling movement of saiD rollers between said cam surfaces and said surfaces on said jaws following initial engagement of said jaws with said pipe.
 13. In a tong as defined in claim 12, said resilient means comprising bodies of resiliently deformable material, said rollers having shafts engaged by said bodies.
 14. In a tong as defined in claim 13, said bodies of resiliently deformable material being composed by polyurethane.
 15. In a tong as defined in claim 12, said rollers having shafts, shoes slidably supported by said jaws and engaged with said shafts, and said resilient means comprises springs acting on said shoes.
 16. In a tong assembly as defined in claim 12, said rollers having shafts having end portions projecting from said rollers, said jaws having slots into which said ends of said rollers extend, and said resilient means being disposed in said slots and acting on the ends of said shafts. 